This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-245812, filed Aug. 14, 2000; and No. 2001-020183, filed Jan. 29, 2001, the entire contents of both of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a silver halide color photographic lightsensitive material and a novel color coupler compound used therein.
2. Description of the Related Art
Many photographic couplers are used as they are dispersed in high-boiling organic solvents such as phosphoric ester and phthalic ester. On the other hand, lightsensitive materials for photographing are required to be thin in order to improve the sharpness. Therefore, couplers used in lightsensitive materials for photographing are dispersed by emulsification by using no high-boiling organic solvents (so-called oilless dispersion) or by using only slight amounts of high-boiling organic solvents. Compared to a case in which high-boiling organic solvents are used, the color forming efficiency lowers, and the absorption spectrum broadens.
Also, silver halide color photographic lightsensitive materials are strongly required to have faithful color reproducibility in addition to high sensitivity, high sharpness, and high granularity.
In the field of silver halide color photographic lightsensitive materials, a 1-phenyl-5-pyrazolone coupler has been conventionally widely used as a magenta coupler. On the other hand, some pyrazoloazole-based couplers having little side absorption and good hue, which are favored as image forming dyes, have been put into practical use.
Pyrazolotriazole magenta couplers are excellent compounds in that they have good hue. However, when introduced into lightsensitive materials, they pose various problems such as low color forming efficiency, low resistance against processing variations, and low color image storage stability.
In particular, a 4-equivalent pyrazolotriazole magenta coupler which couples with an oxidized form of an aromatic primary amine developing agent in the position of hydrogen atom substitution has low color forming efficiency, although it has high granularity, and has a large degree of yellow coloration which occurs by the lapse of time after development. On the other hand, a 2-equivalent coupler whose coupling position is substituted by a split-off group (e.g., a halogen atom) except for a hydrogen atom generates a color with a smaller silver amount than a 4-equivalent coupler. Although this 2-equivalent coupler does not easily cause yellow coloration, the granularity lowers, and this degrades the image quality.
To solve these problems, couplers in which substituents on pyrazoloazole rings are variously improved have been proposed. For example, U.S. Pat. No. 4,882,266 and European Patent Publication No. 183,445 disclosed improvements of the light fastness of a color image by couplers in which the bulkiness of a 6-position substituent is increased. Jpn. Pat. Appln. KOKAI Publication No. (hereinafter referred to as JP-A-)1-102557 disclosed improvements of the color forming efficiency in oilless processing by couplers in which carboxylic acid is introduced as a dissociation group into coupler molecules. JP-A-5-150419 describes a coupler having a sulfonamide bond. JP-A-63-291058 also describes a coupler similar to the present invention. Unfortunately, when the present inventors attempted to apply these techniques, they newly found that improvements of yellow coloration and color image storage stability by these techniques during the lapse of time after processing were still unsatisfactory. Also, they newly found that the couplers increased the cost and deteriorated the crystallinity and hence could not be used in industrial applications. Furthermore, they newly found that the sensitivity decreased when the couplers were retained before coating after they were mixed in color-sensitized silver halide emulsions.
Most pyrazoloazole-based couplers currently put into practical use are 2-equivalent couplers having a split-off group except for a hydrogen atom in a portion where these couplers react with an oxidized form of a color developing agent. Color reversal photographic lightsensitive materials are subjected to first development, reversal processing, and color development in this order. 2-equivalent couplers have an essential problem that since they have high color forming efficiency per mol of silver, they decrease the sensitivity compared to 4-equivalent couplers. Therefore, when pyrazoloazole magenta couplers are to be applied to color reversal photographic lightsensitive materials, 4-equivalent couplers are preferred in respect of sensitivity. From this viewpoint, the couplers described in JP-A""s-5-150419 and 63-291058 are unfavorable because they are primarily 2-equivalent couplers. Applications of 4-equivalent pyrazoloazole magenta couplers to color reversal photographic lightsensitive materials are described in, e.g., JP-A""s-5-100382 and 63-153548. However, these techniques have not solved the above-mentioned problem of yellow coloration caused by the lapse of time after processing. In addition, the problem of the absorption spectrum of a generated dye in oilless dispersion remains unsolved.
It is the first object of the present invention to provide a silver halide color photographic lightsensitive material which has high color reproducibility and high image stability and produces stains little. It is the second object of the present invention to provide a coupler which achieves high color forming efficiency even when the use amount of a high-boiling organic solvent is reduced. It is the third object of the present invention to provide a novel pyrazolotriazole-based compound which can be manufactured at low cost and has high manufacturing suitability. It is the fourth object of the present invention to provide a silver halide color photographic lightsensitive material which lowers the sensitivity little when stored and changes photographic properties little by variations in processing compositions.
The present inventors made extensive studies on the structure and photographic properties of pyrazolotriazole couplers. As a consequence, the present inventors have found couplers solving the above problems and thereby completed the present invention.
That is, the objects of the present invention were achieved by the following lightsensitive material and compound.
(1) A silver halide color photographic lightsensitive material comprising at least one photosensitive silver halide emulsion layer on a support, wherein the emulsion layer contains a magenta coupler represented by formula (M-1) below: 
wherein R1 represents a substituted or nonsubstituted alkyl group; each of L1 and L2 independently represents a substituted or nonsubstituted alkylene group, or substituted or nonsubstituted arylene group; in xe2x80x94L3xe2x80x94G, L3 represents xe2x80x94NHxe2x80x94SO2xe2x80x94 or xe2x80x94SO2xe2x80x94NHxe2x80x94COxe2x80x94 (in these representations, bonding direction is not defined) and G represents a substituted or nonsubstituted alkyl group or substituted or nonsubstituted aryl group, alternatively xe2x80x94L3xe2x80x94G represents xe2x80x94COOH or OH; X represents a hydrogen atom or a group which splits off when coupling with an oxidized form of a developing agent; n represents 1 or 2, when L2 is an alkylene group, or n represents an integer from 1 to 5, when L2 is an arylene group; and a plurality of xe2x80x94L3xe2x80x94G""s can be the same or different, when n is 2 or more.
(2) A silver halide color photographic lightsensitive material comprising at least one photosensitive silver halide emulsion layer on a support, wherein the emulsion layer contains a magenta coupler represented by formula (M-2) below: 
wherein R11 represents a 1- to 6-carbon nonsubstituted alkyl group; L11 represents a 1 to 6-carbon nonsubstituted alkylene group; each of G1 and G2 independently represents a substituted or nonsubstituted alkyl group, substituted or nonsubstituted alkoxy group, substituted or nonsubstituted aryloxy group, halogen atom, substituted or nonsubstituted acylamino group, substituted or nonsubstituted alkoxycarbonyl group, or substituted or nonsubstituted aminocarbonyl group; s represents an integer from 0 to 4; t represents an integer from 0 to 5; u represents 1 or 2; the sum of s and u does not exceed 5; and the value of pKa of xe2x80x94NHSO2xe2x80x94 between the two phenyl groups at 25xc2x0 C. in a solution of THF/H2O=6/4 is 12 or less.
(3) A compound represented by formula (M-3) below: 
wherein each of G11 and G12 independently represents a 1- to 30-carbon, substituted or nonsubstituted alkyl group, 1- to 30-carbon, substituted or nonsubstituted alkoxy group, 6- to 30-carbon, substituted or nonsubstituted aryloxy group, halogen atom, 1- to 30-carbon, substituted or nonsubstituted acylamino group, 2- to 30-carbon, substituted or nonsubstituted alkoxycarbonyl group, or 1- to 30-carbon, substituted or nonsubstituted aminocarbonyl group; sxe2x80x2 represents an integer from 0 to 4; txe2x80x2 represents an integer from 0 to 5; uxe2x80x2 represents 1 or 2; and the sum of sxe2x80x2 and uxe2x80x2 does not exceed 5.
A magenta coupler of the present invention is a novel compound and shows very high performance even in a color negative photographic lightsensitive material. Also, a magenta coupler of the present invention is useful not only as a coupler for a silver halide photographic lightsensitive material but also as a material intermediate of medicines and agricultural chemicals.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
The present invention will be described in detail below. In this specification, xe2x80x9cnonsubstituted alkyl groupsxe2x80x9d mean straight-chain, branched, and cyclic alkyl groups, e.g., an n-butyl group, 2-ethylhexyl group, t-butyl group, and cyclohexyl group. xe2x80x9cSubstituted alkylxe2x80x9d will be described in detail below.
The present invention provides a silver halide color photographic lightsensitive material comprising at least one silver halide emulsion layer on a support, wherein at least one of the emulsion layers contains a magenta coupler represented by formula (M-1) below. 
In formula (M-1), R1 represents a substituted or nonsubstituted alkyl group. R1 is preferably a 1- to 30-carbon, substituted or nonsubstituted alkyl group. Examples of a substituent for substituting this alkyl group are an aryl group, heterocyclic group, acyl group, acyloxy group, acylamino group, alkoxy group, aryloxy group, heterocyclic oxy group, alkoxycarbonyl group, aryloxycarbonyl group, a heterocyclic oxycarbonyl group, alkylcarbamoyl group, arylcarbamoyl group, alkylsulfonyl group, arylsulfonyl group, alkylsulfamoyl group, arylsulfamoyl group, alkylsulfonylamino group, amino group (including an anilino group), alkylsulfinyl group, arylsulfinyl group, alkylthio group, arylthio group, mercapto group, hydroxyl group, cyano group, nitro group, hydroxyamino group, carboxyl group, sulfo group, and halogen atom. Practical examples are those enumerated as substituents for substituting L1 and L2 to be described later. Practical examples of the heterocyclic oxycarbonyl group, alkylcarbamoyl group, arylcarbamoyl group, alkylsulfamoyl group, and arylsulfamoyl group are furyloxycarbonyl, methylcarbamoyl, phenylcarbamoyl, dimethylsulfamoyl, and phenylsulfamoyl, respectively. Examples of R1 are methyl, ethyl, n-propyl, isopropyl, t-butyl, n-octyl, eicosyl, 2-chloroethyl, 2-cyanoethyl, and 2-ethylhexyl. R1 is particularly preferably an alkyl group not containing a hetero atom, i.e., an alkyl group made up of only carbon atoms and hydrogen atoms, and more preferably a 1- to 10-carbon, straight-chain, branched, or cyclic, nonsubstituted alkyl group. R1 is more preferably a 1- to 6-carbon, nonsubstituted alkyl group, further preferably isopropyl or t-butyl, and most preferably t-butyl.
In formula (M-1), L1 represents a substituted or nonsubstituted alkylene group or substituted or nonsubstituted arylene group. Examples of a substituent when this alkylene group or arylene group is substituted are a halogen atom, alkyl group (including a cycloalkyl group), aryl group, heterocyclic group, cyano group, hydroxyl group, nitro group, carboxyl group, alkoxy group, aryloxy group, silyloxy group, heterocyclic oxy group, acyloxy group, carbamoyloxy group, alkoxycarbonyloxy group, aryloxycarbonyloxy group, amino group (including an anilino group), acylamino group, aminocarbonylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfamoylamino group, alkylsulfonylamino and arylsulfonylamino groups, mercapto group, alkylthio group, arylthio group, heterocyclic thio group, sulfamoyl group, sulfo group, alkylsulfinyl and arylsulfinyl groups, alkylsulfonyl and arylsulfonyl groups, acyl group, aryloxycarbonyl group, alkoxycarbonyl group, carbamoyl group, arylazo and heterocyclic azo groups, imide group, phosphino group, phosphinyl group, phosphinyloxy group, phosphinylamino group, and silyl group.
More specifically, examples of the substituent are as follows:
a halogen atom (e.g., a chlorine atom, bromine atom, and iodine atom);
alkyl group {a straight-chain, branched, or cyclic alkyl group, more specifically, a substituted or nonsubstituted alkyl group having preferably 1 to 40 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl, t-butyl, n-octyl, n-octadecyl, eicosyl, 2-chloroethyl, 2-cyanoethyl, and 2-ethylhexyl), substituted or nonsubstituted cycloalkyl group having preferably 3 to 40 carbon atoms (e.g., cyclohexyl, cyclopentyl, and 4-n-dodecylcyclohexyl), bicycloalkyl group (preferably a 5- to 30-carbon, substituted or nonsubstituted bicycloalkyl group, i.e., a monovalent group obtained by removing one hydrogen atom from 5- to 30-carbon bicycloalkane, e.g., bicyclo[1,2,2]heptane-2-yl and bicyclo[2,2,2]octane-3-yl), and group of tricyclo structure having a larger number of ring structures. An alkyl group in substituents to be explained below (e.g., an alkyl group in an alkylthio group) also represents an alkyl group having this concept};
aryl group (preferably a 6- to 50-carbon, substituted or nonsubstituted aryl group, e.g., phenyl, p-tolyl, naphthyl, m-chlorophenyl, o-hexadekanoylaminophenyl, and p-tert-octylphenyl);
heterocyclic group {preferably a monovalent group obtained by removing one hydrogen atom from a 5- or 6-membered, substituted or nonsubstituted, aromatic or nonaromatic heterocyclic compound, an aromatic ring such as benzene being able to be condensed, and more preferably a 3- to 30-carbon, 5- or 6-membered aromatic heterocyclic group. A heterocyclic ring preferably has at least one nitrogen atom, at least one oxygen atom, or at least one sulfur atom, and more preferably has at least one nitrogen atom. Examples of the heterocyclic ring are 2-furyl, 2-thienyl, 2-pyrimidinyl, and 2-benzothiazolyl. A heterocyclic group in substituents to be explained below (e.g., a heterocyclic group in a heterocyclic oxy group) also represents a heterocyclic group having this concept};
cyano group;
hydroxyl group;
nitro group;
carboxyl group;
alkoxy group (preferably a 1- to 30-carbon, substituted or nonsubstituted alkoxy group, e.g., methoxy, ethoxy, isopropoxy, t-butoxy, n-octyloxy, and 2-methoxyethoxy);
aryloxy group (preferably a 6- to 30-carbon, substituted or nonsubstituted aryloxy group, e.g., phenoxy, 2-methylphenoxy, 4-t-butylphenoxy, 3-nitrophenoxy, and 2-tetradecanoylaminophenoxy);
silyloxy group (preferably a 3- to 20-carbon silyloxy group, e.g., trimethylsilyloxy and t-butyldimethylsilyloxy);
heterocyclic oxy group (preferably a 2- to 30-carbon, substituted or nonsubstituted heterocyclic oxy group, e.g., 1-phenyltetrazole-5-oxy and 2-tetrahydropyranyloxy);
acyloxy group (preferably a formyloxy group, 2- to 30-carbon, substituted or nonsubstituted alkylcarbonyloxy group, and 7- to 30-carbon, substituted or nonsubstituted arylcarbonyloxy group, e.g., formyloxy, acetyloxy, pivaloyloxy, stearoyloxy, benzoyloxy, and p-methoxyphenylcarbonyloxy);
carbamoyloxy group (preferably a 1- to 30-carbon, substituted or nonsubstituted carbamoyloxy group, e.g., N,N-dimethylcarbamoyloxy, N,N-diethylcarbamoyloxy, morpholinocarbonyloxy, N,N-di-n-octylcarbamoyloxy, and N-n-octylcarbamoyloxy);
alkoxycarbonyloxy group (preferably a 2- to 30-carbon, substituted or nonsubstituted alkoxycarbonyloxy group, e.g., methoxycarbonyloxy, ethoxycarbonyloxy, t-butoxycarbonyloxy, and n-octylcarbonyloxy);
aryloxycarbonyloxy group (preferably a 7- to 30-carbon, substituted or nonsubstituted aryloxycarbonyloxy group, e.g., phenoxycarbonyloxy, p-methoxyphenoxycarbonyloxy, and p-(n-hexadecyloxy)phenoxycarbonyloxy);
amino group (preferably an amino group, 1- to 30-carbon, substituted or nonsubstituted alkylamino group, and 6- to 30-carbon, substituted or nonsubstituted anilino group, e.g., amino, methylamino, dimethylamino, anilino, N-methyl-anilino, and diphenylamino);
acylamino group (preferably a formylamino group, 2- to 30-carbon, substituted or nonsubstituted alkylcarbonylamino group, and 7- to 30-carbon, substituted or nonsubstituted arylcarbonylamino group, e.g., formylamino, acetylamino, pivaloylamino, lauroylamino, benzoylamino, and 3,4,5-tri-(n-octyloxy)phenylcarbonylamino);
aminocarbonylamino group (preferably 1- to 30-carbon, substituted or nonsubstituted aminocarbonylamino, e.g., carbamoylamino, N,N-dimethylaminocarbonylamino, N,N-diethylaminocarbonylamino, and morpholinocarbonylamino);
alkoxycarbonylamino group (preferably a 2- to 30-carbon, substituted or nonsubstituted alkoxycarbonylamino group, e.g., methoxycarbonylamino, ethoxycarbonylamino, t-butoxycarbonylamino, n-octadecyloxycarbonylamino, and N-methyl-methoxycarbonylamino);
aryloxycarbonylamino group (preferably a 7- to 30-carbon, substituted or nonsubstituted aryloxycarbonylamino group, e.g., phenoxycarbonylamino, p-chlorophenoxycarbonylamino, and m-(n-octyloxy)phenoxycarbonylamino);
sulfamoylamino group (preferably a 0- to 30-carbon, substituted or nonsubstituted sulfamoylamino group, e.g., sulfamoylamino, N,N-dimethylsulfamoylamino, and N-n-octylsulfamoylamino);
alkylsulfonylamino and arylsulfonylamino groups (preferably 1- to 30-carbon, substituted or nonsubstituted alkylsulfonylamino and 6- to 30-carbon, substituted or nonsubstituted arylsulfonylamino, e.g., methylsulfonylamino, butylsulfonylamino, phenylsulfonylamino, 2,3,5-trichlorophenylsulfonylamino, and p-methylphenylsulfonylamino);
mercapto group;
alkylthio group (preferably a 1- to 30-carbon, substituted or nonsubstituted alkylthio group, e.g., methylthio, ethylthio, and n-hexadecylthio);
arylthio group (preferably 6- to 30-carbon, substituted or nonsubstituted arylthio, e.g., phenylthio, p-chlorophenylthio, and m-methoxyphenylthio);
heterocyclic thio group (preferably a 2- to 30-carbon, substituted or nonsubstituted heterocyclic thio group, e.g., 2-benzothiazolylthio and 1-phenyltetrazole-5-ylthio);
sulfamoyl group (preferably a 0- to 30-carbon, substituted or nonsubstituted sulfamoyl group, e.g., N-ethylsulfamoyl, N-(3-dodecyloxypropyl)sulfamoyl, N,N-dimethylsulfamoyl, N-acetylsulfamoyl, N-benzoylsulfamoyl, and N-(Nxe2x80x2-phenylcarbamoyl)sulfamoyl);
sulfo group;
alkylsulfinyl and arylsulfinyl groups (preferably a 1- to 30-carbon, substituted or nonsubstituted alkylsulfinyl group and 6- to 30-carbon, substituted or nonsubstituted arylsulfinyl group, e.g., methylsulfinyl, ethylsulfinyl, phenylsulfinyl, and p-methylphenylsulfinyl);
alkylsulfonyl and arylsulfonyl groups (preferably a 1- to 30-carbon, substituted or nonsubstituted alkylsulfonyl group and 6- to 30-carbon, substituted or nonsubstituted arylsulfonyl group, e.g., methylsulfonyl, ethylsulfonyl, phenylsulfonyl, and p-methylphenylsulfonyl);
acyl group (preferably a formyl group, 2- to 30-carbon, substituted or nonsubstituted alkylcarbonyl group, 7- to 30-carbon, substituted or nonsubstituted arylcarbonyl group, and 5- to 25-carbon, substituted or nonsubstituted, 5- or 6-membered heterocyclic carbonyl group, e.g., acetyl, pivaloyl, 2-chloroacetyl, stearoyl, benzoyl, p-n-octyloxyphenylcarbonyl, and 2-pyridylcarbonyl);
aryloxycarbonyl group (preferably a 7- to 30-carbon, substituted or nonsubstituted aryloxycarbonyl group, e.g., phenoxycarbonyl, o-chlorophenoxycarbonyl, m-nitrophenoxycarbonyl, and p-t-butylphenoxycarbonyl);
alkoxycarbonyl group (preferably a 2- to 30-carbon, substituted or nonsubstituted alkoxycarbonyl group, e.g., methoxycarbonyl, ethoxycarbonyl, t-butoxycarbonyl, and n-octadecyloxycarbonyl);
carbamoyl group (preferably 1- to 30-carbon, substituted or nonsubstituted carbamoyl, e.g., carbamoyl, N-methylcarbamoyl, N,N-dimethylcarbamoyl, N,N-di-n-octylcarbamoyl, N-(methylsulfonyl)carbamoyl, and a group in which R and Rxe2x80x2 of xe2x80x94CON(R)Rxe2x80x2 bond to form a ring (e.g., a morpholinocarbonyl group));
arylazo and heterocyclic azo groups (preferably a 6- to 30-carbon, substituted or nonsubstituted arylazo group, and 3- to 30-carbon, substituted or nonsubstituted heterocyclic azo group, e.g., phenylazo, p-chlorophenylazo, and 5-ethylthio-1,3,4-thiadiazole-2-ylazo);
imide group (preferably N-succinimide and N-phthalimide);
phosphino group (preferably a 2- to 30-carbon, substituted or nonsubstituted phosphino group, e.g., dimethylphosphino, diphenylphosphino, and methylphenoxyphosphino);
phosphinyl group (preferably a 0- to 30-carbon, substituted or nonsubstituted phosphinyl group, e.g., phosphinyl, dioctyloxyphosphinyl, and diethoxyphosphinyl);
phosphinyloxy group (preferably a 2- to 30-carbon, substituted or nonsubstituted phosphinyloxy group, e.g., diphenoxyphosphinyloxy and dioctyloxyphosphinyloxy);
phosphinylamino group (preferably a 2- to 30-carbon, substituted or nonsubstituted phosphinylamino group, e.g., dimethoxyphosphinylamino and dimethylaminophosphinylamino); and
silyl group (preferably a 3- to 30-carbon, substituted or nonsubstituted silyl group, e.g., trimethylsilyl, t-butyldimethylsilyl, and phenyldimethylsilyl).
Of the above functional groups, those having a hydrogen atom can be further substituted by the above groups by removing the hydrogen atom. Examples of such functional groups are an alkylcarbonylaminosulfonyl group, arylcarbonylaminosulfonyl group, alkylsulfonylaminocarbonyl group, and arylsulfonylaminocarbonyl group. More specific examples are methylsulfonylaminocarbonyl, p-methylphenylsulfonylaminocarbonyl, acetylaminosulfonyl, and benzoylaminosulfonyl groups.
When L1 is an alkylene group, this alkylene group is preferably a 1- to 30-carbon, substituted or nonsubstituted alkylene group which can be straight-chain, branched, or cyclic. This alkylene group is more preferably a 1- to 10-carbon, nonsubstituted alkylene group, and most preferably a 1- to 6-carbon, nonsubstituted alkylene group. Examples are methylene, 1,2-ethylene, 1,3-propylene, 1-methylmethylene, 1,1-dimethylmethylene, 1,1,2,2-tetramethyl-1,2-ethylene, 1,4-butylene, 1,4-cyclohexylene, and 1-phenylmethylene.
When L1 is an arylene group, this arylene group is preferably a 6- to 35-carbon, substituted or nonsubstituted arylene group, and more preferably a 6- to 12-carbon, substituted or nonsubstituted arylene group. Examples are 1,2-phenylene, 1,3-phenylene, 1,4-phenylene, and 2,4,6-trimethyl-1,3-phenylene. L1 is preferably an alkylene group, rather than an arylene group.
Practical examples of L1 are presented below, but the present invention is not limited to these examples. In these formulas, a symbol * indicates the position where L1 bonds to a pyrazoloazole ring. 
In formula (M-1), L2 represents a substituted or nonsubstituted alkylene group or substituted or nonsubstituted arylene group. Examples of a substituent when this alkylene group or arylene group is substituted are those enumerated above as substituents for substituting L1.
When L2 is an alkylene group, this alkylene group is preferably a 1- to 30-carbon, substituted or nonsubstituted alkylene group which can be straight-chain, branched, or cyclic. This alkylene group represented by L2 is more preferably a 1- to 25-carbon, substituted or nonsubstituted alkylene group, and the number of carbon atoms is more preferably 1 to 20. A 1- to 6-carbon, nonsubstituted alkylene group is particularly preferred. Examples are 1,2-ethylene, 1,4-butylene, 1,14-tetradecylene, 1,4-cyclohexylene, 1-phenylmethylene, and 2-ethyl-1,6-cyclohexylene.
When L2 is an arylene group, this arylene group is preferably a 6- to 40-carbon, substituted or nonsubstituted arylene group, and more preferably a 6- to 30-carbon, substituted or nonsubstituted arylene group, and the number of carbon atoms is more preferably 6 to 25. Examples are 1,2-phenylene, 1,3-phenylene, 1,4-phenylene, 2-butoxy-1,5-phenylene, 2-octyloxy-1,5-phenylene, 2-hexadecyloxy-1,5-phenylene, 4-methoxyphenoxy-1,5-phenylene, 4-chloro-1,5-phenylene, 2-methoxyethoxy-1,5-phenylene, 2-hexadecyl-1,5-phenylene, 4-hexadecyl-1,5-phenylene, 4-hexadecyloxy-1,5-phenylene, 2-hexadecyloxy-1,4-phenylene, 2-methylcyclohexyloxy-1,5-phenylene, 2-benzyloxy-1,5-phenylene, and 2-octadecyloxy-1,5-phenylene. The 1-position of any of these arylene groups bonds to the right side of an xe2x80x94L1xe2x80x94NHxe2x80x94COxe2x80x94 group of formula (M-1).
Practical examples of L2 are presented below, but the present invention it not limited to these examples. In these formulas, a symbol * indicates the position where L2 bonds to the right side of an xe2x80x94L1xe2x80x94NHxe2x80x94COxe2x80x94 group of formula (M-1). 
L2 is preferably an arylene group, rather than an alkylene group. Also, L2 is preferably substituted. This substituent is preferably an alkoxy group, aminocarbonyl group, halogen atom, or alkyl group.
L3 represents xe2x80x94NHxe2x80x94SO2xe2x80x94 or xe2x80x94COxe2x80x94NHxe2x80x94SO2xe2x80x94 (In these representations, bonding direction is not defined. More specifically, either the left side or the right side of xe2x80x94NHxe2x80x94SO2xe2x80x94 can bond to L2, or either the left side or the right side of xe2x80x94COxe2x80x94NHxe2x80x94SO2xe2x80x94 can bond to L2). Alternatively, L3xe2x80x94G represents xe2x80x94COOH or xe2x80x94OH.
L3 is preferably xe2x80x94NHxe2x80x94SO2xe2x80x94. The left side of xe2x80x94NHxe2x80x94SO2xe2x80x94 preferably bonds to NHxe2x80x94COxe2x80x94L2, and the right side of xe2x80x94NHxe2x80x94SO2xe2x80x94 preferably bonds to G.
X represents a hydrogen atom or a group which splits off when coupling with an oxidized form of a developing agent. Practical examples are a halogen atom, alkoxy group, aryloxy group, acyloxy group, alkylsulfonyloxy or arylsulfonyloxy group, acylamino group, alkylsulfonylamino or arylsulfonylamino group, alkoxycarbonyloxy group, alkylthio, arylthio, or heterocyclic thio group, carbamoyl group, carbamoyloxy group, heterocyclic carbonyloxy group, 5- or 6-membered, nitrogen-containing heterocyclic group, imide group, arylazo group, and alkyl group {e.g., a group represented by formula xe2x80x94CR21(R22)xe2x80x94NHxe2x80x94SO2xe2x80x94R23 (each of R21 and R22 independently represents a hydrogen atom, substituted or nonsubstituted alkyl group, or substituted or nonsubstituted aryl group, and R23 represents a substituted or nonsubstituted alkyl group or substituted or nonsubstituted aryl group)}.
X is preferably a hydrogen atom, halogen atom, alkoxy group, aryloxy group, alkylthio or arylthio group, alkyloxycarbonyloxy group, aryloxycarbonyloxy group, or carbamoyloxy group, more preferably a hydrogen atom, halogen atom, 6- to 30-carbon arylthio group, or 6- to 30-carbon aryloxy group, and most preferably a hydrogen atom.
G represents a substituted or nonsubstituted alkyl group or substituted or nonsubstituted aryl group. Examples of a substituent for substituting these alkyl and aryl groups are those enumerated above as substituents for substituting L1 and L2. G is preferably a 1- to 30-carbon, substituted or nonsubstituted alkyl group or 6- to 30-carbon, substituted or nonsubstituted aryl group, and more preferably a 6- to 30-carbon, substituted or nonsubstituted aryl group. This aryl group is preferably substituted. This substituent is preferably a 2- to 10-carbon alkoxycarbonyl group (including a cycloalkoxycarbonyl group), an aminocarbonyl group substituted by 1- to 10-carbon alkyl, a halogen atom, or a 1- to 20-carbon alkyl group.
In formula (M-1), n represents 1 or 2 when L2 is an alkylene group, and represents an integer from 1 to 5 when L2 is an arylene group. When n is 2 or more, a plurality of xe2x80x94L3xe2x80x94G""s can be the same or different. n is preferably 1 or 2.
In a preferred structure of formula (M-1), R1 is a 1- to 10-carbon, straight-chain, branched, or cyclic, nonsubstituted alkyl group, L1 is a 1- to 10-carbon, nonsubstituted alkylene group, L2 is a 6- to 30-carbon, substituted or nonsubstituted arylene group, L3 is xe2x80x94NHxe2x80x94SO2xe2x80x94 (the left side bonds to NHxe2x80x94COxe2x80x94L2 and the right side bonds to G), n is 1 or 2, X is a hydrogen atom, halogen atom, 6- to 30-carbon arylthio group, or 6- to 30-carbon aryloxy group, and G is a 6- to 30-carbon, substituted or nonsubstituted aryl group.
A coupler represented by formula (M-1) preferably has a structure represented by formula (M-2) below. 
In formula (M-2), R11 is a 1- to 6-carbon, nonsubstituted alkyl group. Practical examples of R11 are methyl, ethyl, n-propyl, isopropyl, t-butyl, and t-octyl. R11 is preferably isopropyl or t-butyl and most preferably t-butyl.
L11 is a 1- to 6-carbon, nonsubstituted alkylene group. Practical examples are methylene, 1,2-ethylene, 1,3-propylene, 1-methylmethylene, 1-isopropylmethylene, 1,1-dimethylmethylene, 1,1,2,2-tetramethyl-1,2-ethylene, 1,4-butylene, and 1,4-cyclohexylene. L11 is most preferably 1-methylmethylene.
Each of G1 and G2 independently represents a substituted or nonsubstituted alkyl group, substituted or nonsubstituted alkoxy group, substituted or nonsubstituted aryloxy group, halogen atom, substituted or nonsubstituted acylamino group, substituted or nonsubstituted alkoxycarbonyl group (including a cycloalkyloxycarbonyl group), or substituted or nonsubstituted aminocarbonyl group.
G1 is preferably a 1- to 30-carbon, nonsubstituted alkyl group (e.g., methyl or t-octyl), 1- to 30-carbon, nonsubstituted alkoxy group (e.g., methoxy, n-octyloxy, or n-octadecyloxy), 6- to 30-carbon, nonsubstituted aryloxy group (e.g., phenoxy or p-methoxyphenoxy), or 2- to 31-carbon alkoxycarbonyl group (e.g., methoxycarbonyl, n-octyloxycarbonyl, or n-octadecyloxycarbonyl). G1 is most preferably a 1- to 22-carbon, nonsubstituted alkoxy group.
It is preferable that G1 bond to the phenylene group in an ortho-position to xe2x80x94L11xe2x80x94NHxe2x80x94COxe2x80x94 in formula (M-2).
G2 is preferably a halogen atom (e.g., chlorine, bromine, or iodine), 1- to 30-carbon, nonsubstituted acylamino group (e.g., formylamino, acetylamino, or pivaloylamino), 2- to 30-carbon, nonsubstituted alkoxycarbonyl group (e.g., methoxycarbonyl, ethoxycarbonyl, n-octyloxycarbonyl, or cyclohexyloxycarbonyl), or 1- to 30-carbon aminocarbonyl group which is nonsubstituted or substituted by an alkyl group (e.g., carbamoyl, dimethylcarbamoyl, n-octylcarbamoyl, or piperidinocarbonyl). G2 is most preferably a 2- to 10-carbon, nonsubstituted alkoxycarbonyl group or 2- to 10-carbon aminocarbonyl group substituted by an alkyl group.
When t is 1, it is preferable that G2 bond to the phenyl group in a meta-position to xe2x80x94NHxe2x80x94SO2xe2x80x94 in formula (M-2). When t is 2, it is preferable that two G2""s bond to the phenyl group in two meta-positions to xe2x80x94NHxe2x80x94SO2xe2x80x94 in formula (M-2).
s represents an integer from 0 to 4, t represents an integer from 0 to 5, and u represents 1 or 2. The sum of s and u does not exceed 5. s is preferably 0 or 1, t is preferably 1 or 2, and u is preferably 1.
In a magenta coupler represented by formula (M-2), the value of pKa of xe2x80x94NHSO2xe2x80x94 between the two phenyl groups at 25xc2x0 C. in a solution of THF/H2O=6/4 is 12 or less, preferably 11 or less. This pKa is preferably 5 or more, more preferably 7 or more, and most preferably 9 or more.
The pKa is preferably 5 to 12, more preferably 7 to 11, and most preferably 9 to 10.5.
In a magenta coupler represented by formula (M-2), when both substituents G1 and G2 of the phenyl groups are alkyl groups or alkoxy groups, the value of pKa exceeds 12.
A coupler having a pKa value of 12 or less has high color forming efficiency even when used without any oil, and has a small effect on the color forming efficiency caused by variations in the pH of a processing solution.
In practical examples CP-2 and CP-5 to be presented later of a magenta coupler, pKa values are 10.4 and 10.9, respectively.
In formula (M-2), the left side of xe2x80x94NHxe2x80x94SO2xe2x80x94 bonds to the phenyl group in arbitrary position to form the phenylene group. Preferably, the left side of xe2x80x94NHxe2x80x94SO2xe2x80x94 bonds to the phenyl group in a meta-position to xe2x80x94L11xe2x80x94NHxe2x80x94COxe2x80x94 in formula (M-2).
A coupler having a structure represented by formula (M-1) of the present invention more preferably has a structure represented by formula (M-3) below. A coupler having this structure is a novel compound. 
In formula (M-3), each of G11 and G12 independently represents a 1- to 30-carbon, substituted or nonsubstituted alkyl group, 1- to 30-carbon, substituted or nonsubstituted alkoxy group, 6- to 30-carbon, substituted or nonsubstituted aryloxy group, halogen atom, 1- to 30-carbon, substituted or nonsubstituted acylamino group, 2- to 30-carbon, substituted or nonsubstituted alkoxycarbonyl group, or 1- to 30-carbon, substituted or nonsubstituted aminocarbonyl group. Practical examples of substituents G11 and G12 are those enumerated above for G1 and G2 in formula (M-2).
G11 is preferably a 1- to 30-carbon, substituted or nonsubstituted alkyl group, 1- to 30-carbon, substituted or nonsubstituted alkoxy group, or 6- to 30-carbon, substituted or nonsubstituted aryloxy group. G11 is more preferably a 1- to 22-carbon, nonsubstituted alkoxy group, and most preferably n-hexadecyloxy, n-octadecyloxy, n-eicosyloxy, or n-dieicosyloxy.
It is preferable that G11 bond to the phenylene group in an ortho-position to xe2x80x94CH(CH3)xe2x80x94NHxe2x80x94COxe2x80x94 in formula (M-3).
G12 is preferably a halogen atom, 1- to 30-carbon, substituted or nonsubstituted acylamino group, 2- to 30-carbon, substituted or nonsubstituted alkoxycarbonyl group, or 1- to 30-carbon, substituted or nonsubstituted aminocarbonyl group. G12 is more preferably a 2- to 10-carbon, nonsubstituted alkoxycarbonyl group or 2- to 10-carbon, nonsubstituted alkylaminocarbonyl group.
When txe2x80x2 is 1, it is preferable that G12 bond to the phenyl group in a meta-position to xe2x80x94NHxe2x80x94SO2xe2x80x94 in formula (M-3). When txe2x80x2 is 2, it is preferable that two G12""s bond to the phenyl group in two meta-positions to xe2x80x94NHxe2x80x94SO2xe2x80x94 in formula (M-3).
sxe2x80x2 represents an integer from 0 to 4, txe2x80x2 represents an integer from 0 to 5, and uxe2x80x2 represents 1 or 2. The sum of sxe2x80x2 and uxe2x80x2 does not exceed 5. sxe2x80x2 is preferably 0 or 1, txe2x80x2 is preferably 1 or 2, and uxe2x80x2 is preferably 1.
In formula (M-3), the left side of xe2x80x94NHxe2x80x94SO2xe2x80x94 bonds to the phenyl group in arbitrary position to form the phenylene group. Preferably, the left side of xe2x80x94NHxe2x80x94SO2xe2x80x94 bonds to the phenyl group in a meta-position to xe2x80x94CH(CH3)xe2x80x94NHxe2x80x94COxe2x80x94 in formula (M-3).
The measurement of the pKa value in the present invention will be described below. The pKa value was measured under the following conditions by using the AT-210 measurement device (Kyoto Denshi Kogyo K.K.) That is, 1xc3x9710xe2x88x925 mL of a magenta coupler of the present invention was accurately weighed at room temperature (25xc2x0 C.) and dissolved in 30 mL of THF. 20 mL of H2O were then added to completely dissolve the material. Subsequently, 0.25 mL of an aqueous 0.2 N hydrochloric acid solution was added, and the resultant solution was stirred. This solution was titrated with an aqueous 0.2 N NaOH solution, and the pKa value was obtained from the middle point of neutralization. All pKa values in the present invention were obtained under the above measurement conditions.